In many cases of treating a lesion in an intravital tract, such as removing cholesterol or anything else that has accumulated in a blood vessel or removing gallstones in the gall duct, the substance concerned is removed from the wall surface of the tract. Where a blood vessel is to be so treated, these pieces of the removed substance will be carried by the blood flow and may block thinner blood vessels downstream.
According to a technique to address this problem disclosed in JP2001-212152A (hereinafter referred to as Patent Reference 1), a filter is temporarily arranged in the tract by inserting a wire provided with a capture filter, and such potentially embolic material is captured by the filter.
The capture filter according to Patent Reference 1 comprises a cage body composed by joining three or more linear alloy wires with one another at both front and rear ends and swelling midway parts of the plurality of alloy wires in the radial direction to arrange them along a substantially football-shaped border face, and an umbrella-shaped cover is formed by covering with an elastic membrane the part of the outer surface of that cage body, for instance, from the front end to substantially the middle point; embolic material is captured by that umbrella-shaped cover.
The wire is inserted into a leading catheter, and the capture filter in a state of being kept folded is inserted together with the leading catheter into a blood vessel. When they reach the target region, the front end of the wire is fed out forward from the leading catheter to let out the capture filter from the leading catheter into the aforementioned shape of swelling in the radial direction.
However, in the wire for insertion into intravital tracts, as the umbrella-shaped cover consisting of a membrane constitute the filter to capture embolic material, there is a fear that the umbrella-shaped cover itself may obstruct blood circulation in the blood vessel. There is a version in which many holes are bored in that membrane, but this still involves a fear of failure to ensure a sufficient blood stream.
Further, to consider a state in which capture filter is folded, the diameter of the capture filter will be increased by the thickness of the membrane doubled by the folding, and the filter will become correspondingly less adaptive to thin tracts.
An object of the present invention, attempted in view of these problems, is to provide a wire for insertion into intravital tracts whose diameter can be reduced without sacrificing the smoothness of the stream within the tract.